1. Field of the Invention
The present invention relates to a method and system for determining interference fit of a weather strip interposed between movable and immovable closure panels of vehicle so as to enable adjustments intended to minimize air and water leaks between the panels and their corresponding mating surfaces.
2. Disclosure Information
Wind noise around the doors and windows of motor vehicles is a frequent source of dissatisfaction for motorists. Wind noise arises from air passing through the door and weather strip interfaces. Motion of the vehicle creates a pressure differential between the vehicle interior and exterior which increases as the vehicle reaches higher speed. This pressure differential causes a flow of air through the interfaces between the closure panels and the weather strips or seals. This leakage is generally referred to as an “aspiration leak”. FIG. 1 is a stylized representation of a body structure, 10, having a movable closure panels 12 and first plurality of weather strip seals 14 and a second plurality of weather strip seals 16. Weather strips 14 of FIG. 1 leak because closure panel 12 does not compress seal 14 sufficiently so as to prevent a leakage path between body 10 and seal 14. On the other hand, closure panel 13 compresses seal 16 sufficiently to create an interference fit between seal 16 and body 10. As a result, no aspiration leak will exist between closure panel 13 and body 10, or more precisely, between seal 16 and body 10.
The purpose of the present invention is to provide a method and measurement system to identify and quantify correct fit of weather strips, which is achieved when there is interference between the weather strip and the panel or body surface to which it is sealing. In essence, the present invention provides a “interference indicator tape” (IIT) which can be used to reduce interference variability of dynamic seals such as weather strips on the doors of vehicles as well as other movable closure panels such as moon roofs and deck lid and engine compartment hoods. IIT may also be used to reduce wind and water leaks and to fit closure panels such as windshields and backlites.
Automotive designers and engineers have used a variety of tests to determine the presence and source of weather strip leaks. Once such test is called the chalk test. This involves spraying chalk from an aerosol can onto a vehicle weather strip. Then the door is closed and opened and presence of transferred chalk is noted. Unfortunately the chalk test Is unreliable because the amount of chalk transferred from the weather strip to the door depends to a very great extent on the normal force developed between the weather strip and the vehicle body or door. Also, the sprayed chalk flies everywhere and is extremely difficult to remove from the vehicle. This type of test is therefore not appropriate for customer vehicles or vehicles being produced in assembly plants.
A second type of prior art test involves a thin film which when trapped between the weather strip and the closure panel changes color in relation to the pressure being applied. Unfortunately, such films do not work at the low normal pressures generally needed to properly engineer and provide automotive weather strips.
As might be imagined, electronic pressure measuring devices such as thin film tactile pressure sensors may be used to determine the normal force between a weather strip and a vehicle closure panel or body. Unfortunately, such systems are plagued with low resolution, very great expense, extraordinary time demands upon the human operator, and difficulties in reproducing the study results because of the need to precisely determine locations where measurements are taken.
Other type of tests for weather strips include air leakage testing which, although allowing measurement of the gross amount of air escaping from a passenger cabin, cannot pinpoint the location of an air leak. Although ultrasonic testing may be used to prevent severe weather strip leaking from occurring, it is very difficult to relate the ultrasonic result to the severity of the weather strip gaps, if any. Finally, sealing gaps are often measured in a vehicle body before the installation of weather strips. However, such gaps do not typically correlate well with the weather strip gaps experienced on vehicles. This lack of correlation may arise from the inability to precisely predict the free standing height and characteristic of seals. Electronic sound measurement devices are also used to analyze wind noise. However, such devices cannot locate the source of the wind noise with the precision needed to adjust the seal interference to achieve a desired reduction wind noise.
A method and system according to present invention solves the problems associated with prior art seal interference and leakage path detection systems, at a low cost and without the need for more than minimal training of personnel employing the present system and method.